Direct effects and indirect interactions between flea beetles and cinnabar moths on the ragwort
| MSI99P1261 | |
| Ganeshan, S. | |
| Imperial College of Science, Technology and Medicine, Silwood Park, Ascot, UK | |
| Direct effects and indirect interactions between flea beetles and cinnabar moths on the ragwort | |
| Thesis, M.Sc., Applied Entomology | |
| Thesis | |
| 1992 | |
| 69 p., 7 appen., 21 tbls. | |
| En | |
| En | |
| A variety of manipulative field studies were carried out on the interactions between the principal invertebrate herbivores of ragwort. The aim was to determine the extent to which the insects affected plant performance, and the degree to which insect-insect interactions were mediated through host plant effects. It was found that ragwort plants with enhanced levels of flea beetle larvae on their roots were preferred by ovipositing cinnabar moths. Laboratory studies of regeneration from root fragments showed that roots from plants which flowered last year produced fewer regrowths than plants flowering this year and plants which were vegetative this year. Gap size in the grassland had a significant impact on the number and survival of seedlings and regrowths from roots. Highest number of regrowths was observed in gap sizes of 20 cm and highest mortality was found inthe no-gap treatment. Larvae of the flea beetle showed a preference for root fragments from this year's flowering and vegetative plants rather than last year's flowering plants in laboratory studies. For roots taken from flowering plants, larvae preferred tha fragments from the top of the root stock. Adult Flea beetles confined to leaves at different levels of the canopy did not show differential feeding but in laboratory studies they did show a preference for leaves of flowering plants over those of vegetative plants. Within flowering plants they preferred leaves from the middle of the canopy. A very low population of the cinnabar moth was observed in the Nash's Field due to the very low ragwort plant density found there. Rabbit exclusion by fencing had a significant impact in reducing the number of ragwort flowering plants. Damage by the flea beetle larvae to the root stock caused wilting in the ragwort under drought conditions. Herbivores and perennial competitors of the ragwort can lead to a crash in the population of the ragwort. | |
| INSECT PESTS WEEDS WEED CONTROL BIOLOGICAL CONTROL | |
| Biological control of weeds | |
| 632.76 | |
| 1992-11-17 | |
| En | |
| Mauritius Sugar Industry Research Institute | |
| LIB | |
| CAT | |
| ENTO |